Anatomy and venous hemodynamics of gait phases

The Valve-Muscular Pump (MVP) of the lower limb, a kind of peripheral heart, is principally activated during walking, by the succession of gait phases. The pump has three parts, which work in a coordinated way.The foot pump, due to the compression of the predominating lateral plantar vein during the contact on the ground (40% of gait event), “eject” 20-30 cm3 of blood into the posterior tibial vein and, in alternative, in the anterior tibial, peroneal and saphenous veins connected by perforators.The distal calf pump, activated during dorsiflexion of the ankle (passive 20% and active 40% of gait event), when the calf muscles are stretched and their distal part descends within the fascial sheath. This movement acts like a piston which expels venous blood in proximal direction.The proximal calf muscle pump due to sural and gastrocnemius muscles rich in venous sinuses that are strongly squeezed during the impulse phase of the step.During dorsiflexion of the ankle (passive or active) space is given to the blood coming from the foot pump (due to weight bearing), that will feed in prevalence the posterior tibial veins. These two systems are “in series”: the foot pump cannot expel the blood into the deep veins if these are not regularly emptied. The proximal pump, at the opposite, is very strong and can void a high volume of blood in the popliteal vein, even in the absence of a favourable gradient as it works “in parallel”.